Properties Of and Changes in Substances
In this unit, students deepen their understanding of the characteristics and properties of substances, and the changes that occur in substances in different situations. Through their explorations, students identify the three states of matter - solids, liquids, and gases - and describe the properties of each. Students observe examples of reversible and non-reversible changes, including changes in state. Students also investigate how the characteristics and properties of substances are altered during physical and chemical changes. Students identify examples of these changes in the world around them. Safety practices related to chemical products in the home are addressed. Students evaluate household products by using criteria such as efficiency, cost, and environmental impact.
Interactions of Materials
All substances are made of atoms. Each substance and its atomic structure is unique in its properties and characteristics. When atoms of different substances interact, the original properties or characteristics can change. For example, mixing Smarties and Corn Flakes will not change the properties or characteristics of either substance. However, adding on or the other to milk, acid, lemon juice, or all three would change it's properties and characteristics. The changes may be quick and easy to observe (e.g. adding ice cream to a soft drink causes the ice cream to melt and mix with the soda), or very slowly and difficult to observe (e.g. leaving newspaper in the air causes it to turn yellow and become brittle over time).
All substances are made of atoms. Each substance and its atomic structure is unique in its properties and characteristics. When atoms of different substances interact, the original properties or characteristics can change. For example, mixing Smarties and Corn Flakes will not change the properties or characteristics of either substance. However, adding on or the other to milk, acid, lemon juice, or all three would change it's properties and characteristics. The changes may be quick and easy to observe (e.g. adding ice cream to a soft drink causes the ice cream to melt and mix with the soda), or very slowly and difficult to observe (e.g. leaving newspaper in the air causes it to turn yellow and become brittle over time).
| bill+nye+states+of+matter+worksheet.pdf |
What Is Matter?
| why_does_matter_matter.pdf |
What triggers a chemical reaction
Chemical Reactions
Why is popping popcorn a chemical change.
First of all, everything that happens around us is either a chemical or physical change, or sometimes both. In the case of popcorn, you can easily see that a change has happened because the initial product is different from the final product. Also, the popcorn you initially see is different from the popcorn that you eat. It tastes better, too.
Chemical changes in popcorn include the alteration of its chemical contents, for example, the starch contained in the corn now is converted to a more digestible form. It's pretty much the same when you fry an egg: when you break it, the white yolk is transparent, but when it's fried, the white becomes, well, white... and more edible if compared to its previous state.
Physical change is the easiest to observe; it can be seen from the obvious, for example increase in size and colour. Also, it's hot to touch, unlike before you pop it.
First of all, everything that happens around us is either a chemical or physical change, or sometimes both. In the case of popcorn, you can easily see that a change has happened because the initial product is different from the final product. Also, the popcorn you initially see is different from the popcorn that you eat. It tastes better, too.
Chemical changes in popcorn include the alteration of its chemical contents, for example, the starch contained in the corn now is converted to a more digestible form. It's pretty much the same when you fry an egg: when you break it, the white yolk is transparent, but when it's fried, the white becomes, well, white... and more edible if compared to its previous state.
Physical change is the easiest to observe; it can be seen from the obvious, for example increase in size and colour. Also, it's hot to touch, unlike before you pop it.
Why the Ivory Soap experiment is a physical change.
Two processes occur when you microwave the soap. First, you are heating the soap, which softens it. Second, you are heating the air and water trapped inside the soap, causing the water to vaporize and the air to expand. The expanding gases push on the softened soap, causing it to expand and become a foam. Popping popcorn works in much the same way. When you microwave Ivory™, the appearance of the soap is changed, but no chemical reaction occurs. This is an example of a physical change. It also demonstrates Charles' Law, which states the volume of a gas increases with its temperature. The microwaves impart energy into the soap, water, and air molecules, causing them to move faster and further away from each other. The result is that the soap puffs up. Other brands of soap don't contain as much whipped air and simply melt in the microwave.
Two processes occur when you microwave the soap. First, you are heating the soap, which softens it. Second, you are heating the air and water trapped inside the soap, causing the water to vaporize and the air to expand. The expanding gases push on the softened soap, causing it to expand and become a foam. Popping popcorn works in much the same way. When you microwave Ivory™, the appearance of the soap is changed, but no chemical reaction occurs. This is an example of a physical change. It also demonstrates Charles' Law, which states the volume of a gas increases with its temperature. The microwaves impart energy into the soap, water, and air molecules, causing them to move faster and further away from each other. The result is that the soap puffs up. Other brands of soap don't contain as much whipped air and simply melt in the microwave.
Safety With Household Chemicals Assignment
Household products and chemical symbols
| household_products.pdf |
Consumer Hazard Warning Symbols
| whmis_information_(1).pdf |
