Question

1. energy is given off during a chemical reaction because are combining with other
2. during the \try this\ experiment, we see the students using vinegar and salt to clean old copper pennies. the copper gets stripped away and the pennies look new again. explain why you think this happens.
3. when vinegar and baking soda react together, the new substance that is produced is
4. & are both dangerous by themselves, but when they react together they form table salt.
5. pyrotechnician is a name given to people who work to create
6. in another experiment, we see kids blow up a balloon by mixing together vinegar and baking soda. when the kids touch the blown up balloon, it is to the touch. this means that the reaction is endothermic or exothermic
7. when someone gets hurt playing sports, often times a cold pack is used for the injury. the cold pack takes up more energy than it gives off and it gets very to the touch. this means that the reaction taking place is endothermic or exothermic
8. how do you know baking a cake is a chemical reaction?
9. there are naturally occurring elements.
10. if elements are in the same group on the periodic table, what does that tell you?

Explanation:

1. Chemical bonds are broken and formed, releasing energy.
2. Vinegar (acetic acid) and salt (sodium - chloride) react with copper oxide on the penny's surface, dissolving it.
3. When vinegar (acetic acid) and baking soda (sodium bicarbonate) react, carbon dioxide, water, and sodium acetate are produced. The main new substance is carbon dioxide gas.
4. Sodium and chlorine are dangerous alone but form table - salt (sodium chloride) when reacted.
5. Pyrotechnicians create fireworks.
6. When vinegar and baking soda react to blow up a balloon, the reaction is endothermic if the balloon is cold to the touch.
7. A cold - pack reaction is endothermic as it takes in energy and feels cold.
8. Baking a cake is a chemical reaction because new substances (e.g., cooked proteins, carbon - dioxide from leavening agents) are formed, and the process is irreversible.
9. There are 94 naturally occurring elements.
10. Elements in the same group on the periodic table have the same number of valence electrons and similar chemical properties.

Answer:

1. Chemical bonds change, releasing energy.
2. Acid and salt react with copper oxide.
3. Carbon dioxide (and sodium acetate and water).
4. Sodium; Chlorine
5. Fireworks
6. Cold; Endothermic
7. Cold; Endothermic
8. New substances are formed and it's irreversible.
9. 94
10. They have the same number of valence electrons and similar chemical properties.